If anyone wants the panel design in Corel, CAD (DXF), CAD (DWG), or Autosketch (SKF), drop me a line using regular email and I'll send them to you. You can use these files as a basis for your own design, or leave the layout the same and just change the text labels.

Scott, the monitors changed over the years. I don't know how yours worked. The early 70s used four wires (or so, depending on the tank) to light the light bulbs. In the mid 70s that changed to two wires and some resistors, but it was still a pretty simple conductive measurement device. Later, the system measured pressure.

You can buy a new pressure measuring system and install it, since the voltage sent by the transducer can use the same wires that either system (pressure or conductance) used. I don't think the older systems are supported by Airstream any longer.

I have "discovered" a very easy to program microprocessor product from Arduino that can provide a complete monitor system in one small $12 PCB and a small additional PCB to hold the LED level indicators.

This Arduino device has 8 analog inputs, so it can do a lot more than just the tank levels. More to come.

I enjoyed tinkering with the dedicated logic of the monitor described in this thread, but adjusting the resistors to match the input voltages was a true pain and took a lot more time that just changing the voltage levels in software in the Arduino.

If you're interested in replacing your tank monitor, look for a future post titled "Arduino Tank Monitor". This one will be a piece of cake, believe me, compared to using dedicated 7400 logic chips. Not to mention easier to build and cheaper.

Zep

PS--the Arduino can monitor the fresh tank for freezing, watch the battery voltage and current, and record indoor and outdoor temperatures. More on that later, too.

This is the prototype of the digital tank monitor. Note that it has battery volts and amps at the top and tank temperatures for each tank. The full thread on this little beauty might be ready by the New Year--watch for it.

This is the prototype of the digital tank monitor. Note that it has battery volts and amps at the top and tank temperatures for each tank. The full thread on this little beauty might be ready by the New Year--watch for it.